1. Field of the Invention
The present invention relates to a projector.
2. Description of the Related Art
A projector (optical projector) projects light onto a screen (surface subject to light projection) and forms an image on the screen. Unless the optical axis of projected light to the screen from the projector is perpendicular to the surface of the screen, therefore, a distorted image is projected on the screen. To avoid such distortion, ordinary projectors are so designed as to detect the tilt angle of the screen surface with respect to the optical axis of projected light and corrects a video image based on the detected angle to thereby project a distortion-free video image.
One of conventional projectors capable of correcting a video image to eliminate its distortion is, for example, a projector which employs the technique disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2001-339671 (page 3 and FIG. 1). This projector preacquires information on the angle of a screen and sets the acquired information on the angle of the screen as an offset value with respect to the detected horizontal and vertical angles of the projector.
The conventional projector requires that the angle of the screen should be set beforehand in order to correct distortion of a video image. There may however a case where the angle of the screen is unclear or the acquired angle of the screen is wrong at the time a projector projects an image. In such a case, the tilt angle of the screen with respect to the optical axis of projected light from the projector is inaccurate. Therefore, the distortion correction of the conventional projector alone may not be able to accurately correct a video image to eliminate its distortion. If the angle of the screen is inaccurate, it is not possible to correct a video image to eliminate its distortion. Nor is it possible to accurately set the focus of projected light from the projector.